Cable television systems are known which distribute incoming television signals to a number of remote television receivers. Often, a remotely-controlled switching matrix routes the video to the remote television receivers, distribution being carried out at radio frequencies. An example of such a system is described in GB 2 117 210-A.
In the recent past a number of TV tuner cards have become available for insertion into personal computers (PCs) to allow broadcast television programmes to be viewed on the computer monitor, usually via Windows (Microsoft trade mark) or similar graphical user interface software.
Such cards again receive a broadband aerial feed at radio frequencies, which may carry up to 1,000 or more different TV transmissions. These can be selected by the user using, in most cases, a tuning application which is generated in Windows and displayed on the monitor screen. The application window may depict a keypad of which various keys can be selected using a keyboard or a displayed pointer (cursor) controlled by a mouse. Clicking the mouse with the pointer on selected keys causes the chosen station to appear on the screen.
Some of the existing tuner cards have a baseband output which allows a composite TV signal (e.g. PAL, SECAM or NTSC) to be sent via suitable cabling, e.g. 75 ohm TV coax, to a remote outstation employing a computer and monitor. An audio output may also be provided so that accompanying mono or stereo sound can also be sent to the outstation.
The widespread use of this technology has so far been limited by the fact that the remote user is restricted to viewing the broadcast which has been selected at the host computer. Hitherto, the facility to select channels at the outstation has been achieved by providing a direct broadband aerial feed at broadcast frequencies with a separate tuner card at each outstation, but the cost of installing low loss high frequency cabling can be prohibitively high. Another technique makes use of existing data networks, but this involves digitising the video signals with a resulting escalation in cost and a deterioration in the final image.
An aim of the present invention may be viewed as being to provide a broadcast television distribution system which is superior to known.